Commissioning of the ATLAS Transition Radiation Tracker (TRT)

Transcription

1 Commissioning of the ATLAS Transition Radiation Tracker (TRT) 11 th Topical Seminar on Innovative Particle and Radiation Detector (IPRD08) 3 October 2008 bocci@fnal.gov On behalf of the ATLAS TRT community Beam halo Event in TRT Disclaimer: I will cover only few topics of the TRT commissioning, mainly those related to real data taking p1

2 The ATLAS Inner Detector p2

3 The ATLAS Inner Detector The Transition Radiation Tracker (TRT) is a straw based gas detector that serves as the outer tracking chamber and also aids in electron identification (through X-ray identification from the radiation material) p3

4 The Transition Radiation Tracker (TRT) Robust pattern recognition requires large number of on-track measurements Wires should be far enough to each other to avoid closeby correlations Length of wires should be small Measurement accuracy ~ 150mm Light weight construction (X 0 ~10%) Self supporting system to minimize X 0 Detector must be compact Minimum space for electronics Detecting elements inside the radiator medium to minimize detector size and enhance TRD performance Sensitive elements as transparent as possible to soft X-ray TRT Barrel p4

5 The Transition Radiation Tracker (TRT) p5

6 TRT Barrel Layout 3 Layers of modules 32 module per phi sector 72 strawlayers per sector Axial only (no z information) Fanny shape so no radial dead spot About 35 measurement per track p6

7 TRT Endcap Layout 40 plain wheel (each side) 768 straws placed along the radius 4 strawlayers per wheel About 40 measurement for tracks full crossing p7

8 TRT Measurements Two thresholds in order to detect TR signal Since full drift time is ~50ns, signal span 3 bunch crossing 25ns 25ns 25ns p8 Time of the first bit converted to distance using a R-t relation The outcomes of the measurement are: Drift Circle Time of Threshold High threshold flag

9 Timing is Everything!! p9

10 TRT Timing p10

11 Data TRT have been commissioned with data for a long time now Combined Test Beam (essential for TR study) Cosmics on surface in 2006 Cosmics in the pit since August 2007 Cosmics with magnetic field already in August 2008 Beam Events Because of the cosmics trigger acceptance, tracks are mainly in the Barrel However a lot of commissioning work in the endcap too (low statistics) Equally important is the tuning of the daily operation of the detector (shifter task, data transfer, feedback between online and offline, etc ) p11

12 Trigger for Commissioning in the Pit p12

13 M6 Cosmic Runs Already look at the alignment in the pit Internal movement ~50mm p13

14 Cosmics Data First Evidence of Module Deformation (deviation from the rigid body approx.) Rotation as a function of z in the TRT (barrel) TWIST! Deformations (kind and magnitude) cannot be foreseen a priori : only data will tell us p14

15 More Milestone Runs p15

16 More Milestone Runs p16

17 More Milestone Runs p17

18 More Milestone Runs Endcap too! p18

19 TRT Threshold Setting p19

20 Mileston Run with Magnetic Field TRT was the only Inner Detector system operational during the solenoid test in August 08 p20

21 Mileston Run with Magnetic Field TRT was the only Inner Detector system operational during the solenoid test in August 08 Impact on r-t relation calibration p21

22 Beam Data for Journalists! Black Hole or Dark Matter? p22

23 Beam Halo p23

24 Beam Splash Beam splash events: Rough estimate: per straw Unique opportunity to time whole the detector at once in one event! This saves may be months of work. p24

25 Beam Splash Events p25

26 Beam Splash Events p26

27 With the full illumination of the detector the timing can be done with 1 event Beam Splash Events COSMIC DIRECTION Timing derived from cosmics clearly seen When accounted for time of flight, timing was within few ns p27

28 Monitoring Monitoring is an essential component of the detector operation p28

29 Monitoring with Real Data Testing of all the infrastructure in the real data taking scenario (not trivial) Invaluable feedback on which quantities are most useful and need to be watched closely Adjustment/reshuffling of plots for different level of monitoring (shifter, expert,..) p29

30 Monitoring with Real Data Testing of all the infrastructure in the real data taking scenario (not trivial) Invaluable feedback on which quantities are most useful and need to be watched closely Adjustment/reshuffling of plots for different level of monitoring (shifter, expert,..) NEXT STEP: TRT MONITOR ON IPOD! p30

31 Other Aspects of the Commissioning Low Voltage equalization Noise Equalization High rate read out with and w/o 0 suppression Validation of the 0 suppression Validation of mapping (online and offline) Integration of services in monitor system (DCS) Gas Operation (leaking, gas change, etc ) CO2 (straw) and electronics cooling Continuous operation of DAQ, LV, HV, etc Offline reconstruction (see C. Schmitt talk) p31

32 Conclusions TRT started its commissioning in the pit already in summer 2007 and moved to continuous operation since summer 2008 Several Milestone Runs helped the commissioning of all the aspects of the TRT operation A fairly operation stability already achieved, focusing on data quality and quick online/offline feedback Final gas mixture (Xe) finally in place and started to be commissioned (stability, gas leak, calibration, etc ) Plans are now to take as much cosmics as possible with the full Inner Detector subsystems operational and with nominal magnetic field on p32